Crown with improved liner



May 13, 1958 L. F. 0LT ETAL 2,834,498

CROWN WITH IMPROVED LINER Fil6d.F8b. 13, 1957 INVENTORS LEONARD E 0LT ROBERT L. 0LT

ATTORNEYS United States Patent CROWN wirn llVlPROVED LINER Leonard F. Olt, Baltimore, Md., and Robert L. Olt, New

Castle, DeL, assignors to Crown Cork & Seal Company, Inc., Baltimore, Md, a corporation of New York The present invention relates to container closures having novel type liner combinations therein.

Composition cork has long been used as a liner for closure shells. However, cork is attacked by some beverages and other materials commonly packed in containers having closures with cork liners. To prevent the cork from deleteriously alifecting the contents of the container it is conventional in such cases to provide the cork liner with a protective spot. Also, the cork disc being somewhat porous, occasionally the contents of the bottle attack the metal cap, causing metal to be dissolved into the contents.

The adhesives conventionally used with composition cork also are sometimes attacked by the contents of the containers. Additionally, a relatively long baking period is required to properly bond the cork with these conventional adhesives. This long baking requires expensive equipment and considerable floor space and is otherwise economically costly.

It is an object of the present invention to prepare a closure shell having a granular cork liner with a novel bonding agent therefor.

An additional object is to prepare a closure shell having a granular cork liner with a bonding agent which also serves as a protective overall coating for the cork.

A further object is to eliminate the time and space consuming bonding step required when conventional cork adhesives are employed.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

It has now been found that these objects can be obtained by .utilizing a thermoplastic material, preferably polyethylene, as the bonding agent for cork granules in making a closure shell liner.

While the present invention is especially adapted for use with crown type closures, it is also useful with other closures such as screw, lug or press-on type caps for example.

Unless otherwise indicated, the term cork is indicated to include the conventional granulated cork.

The invention will be better understood with reference to the drawings, wherein:

Figure l is a vertical view partially in section showing the presently preferred process for forming a liner in a closure shell according to the invention;

Figure 2 is a view similar to Figure 1 but illustrating an alternative procedure for forming the liner;

Figure 3 is another view similar to Figure 1 illustrating another alternative procedure for forming the liner;

Figure 4 is a fragmentary section of the cap having a liner molded by the process illustrated in Figure 1;

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Figure 5 is a vertical view partially in section showing an alternative method of preparing a cork and polyethylene mixture; and

Figure 6 is a vertical view of still another type of cork and polyethylene blend suitable for use in the invention.

Referring more specifically to the drawings, there is provided a conventional metal crown shell 2 having a fluted skirt 4. The shell can be provided with a conventional lacquer (vinyl chloride-vinyl acetate copolymer) coating 6. In the preferred form of the invention granular cork 8 is placed in the lacquered shell 2. Then a glob of polyethylene 10 is placed on top of the cork. The glob can be of either regular or irregular shape. Thus, it can be in the form of a square cut from polyethylene sheeting. There is also provided a molding punch or plunger 12 having steps 14 and 16 on the molding face thereof. By varying the shape of the plunger, the shape of the liner can be changed to secure optimum sealing efficiency under differing conditions. The plunger 12 also has heating element 18 therein. When the hot plunger 12 comes down on the polyethylene 10, the latter is melted or softened enough that it is dispersed throughout the cork and also forms a protective exterior layer 20 of polyethylene over the cork as shown in Figure 4. The polyethylene is an effective binder for the cork and also adheres well to the vinyl resin lacquer 6. The polyethylene is non-toxic and inert to almost all materials which are placed in containers having closure caps, e. g., it is not attacked by beer, cola drinks or ginger ale. In addition, it has excellent bonding action to the cork and provides an outstanding protective coating.

Instead of placing the glob of polyethylene on top of the granular cork, there can be placed a glob of polyethylene 22 in the metal crown closure shell 2 and granular cork 24 positioned in the shell on top of and around the polyethylene. Then the hot forming plunger 12 is engaged on top of the cork to form the finished liner having the cork particles bonded by the polyethylene.

In the form of the invention illustrated by Figure 3, granules of cork 26 are intermingled with granules of polyethylene 28 of about the same average particle size and the intimate mixture is placed in closure 2 and molded into an overall liner with the aid of heated plunger 12. in this form of the invention the polyethylene also forms an effective bonding agent for the cork.

In the form of the invention shown in Figure 5 the cork is blended with polyethylene by heating the polyethylene to its melting point and while it is in the liquid condition, tumbling it with the cork. This mixture is then passed into tube 40 and metered amounts are dropped into closure 42 to form a mass 44- which can then be molded into a liner with the aid of a forming plunger.

Figure 6 shows a square 46 made of granular cork and polyethylene 50. The granular cork and polyethylene were previously blended in the manner described in connection with the description of Figure 5. However, after blending, the mixture of cork and polyethylene is formed into a sheet or ribbon from which a square is cut from such sheet or ribbon.

in a specific example employing the process of Figure 1 and a conventional crow closure having an internal shell diameter of 1.055 inch, there was placed in the metal shell having a vinyl chloride-vinyl acetate resin lacquer coating, composition cork having a particle size of to inch. On top of the cork particles and approximately in the center of the closure was placed a square of polyethylene sheeting (molecular weight about 18,000). Then a plunger having a temperature of 250 F. was applied at a pressure of 30 lb./sq. in. The polyethylene was softened or melted enough to flow and bind the cork particles and form an overall coating thereon as well as to form a union with the lacquer coating on the metal shell.

In another specific example there was utilized a blend of 75% cork and 25% polyethylene by weight, as described in connection with Figure 5, and then a plunger having a temperature of 250 F. was applied at a pressure of 25 lb./ sq. in. in order to form the liner.

The cork can be varied from 87.5 to of the total of polyethylene and cork by weight.

Any solid polyethylene can be employed; thus it can have a molecular weight of 7,000 or 12,000 or l9,000 or 35,000 or even higher. In place of pure polyethylene, there can be employed mixtures containing polyethylene so long as the polyethylene is the primary constituent thereof.

While polyethylene is the preferred thermoplastic material, any other thermoplastic binder can be employed. For food uses, of course, the material should be nontoxic and of food grade. Typical examples of suitable thermoplastic binders are polyvinyl acetals, e. g., polyvinyl formal and polyvinyl butyral, polyvinyl chloride, polyvinylidene chloride, polystyrene, polymethyl alpha chloroacrylate, polyacrylates and methacrylates, e. g., polymethyl methacryate, polybutyl methacrylate, polymethyl acrylate, polyvinyl acetate, polymeric alpha methyl styrene, polyvinyl toluene, polypropylene, polyacrylonitrile and polyisobutylene, copolymers of these materials with each other or with other copolymerizable compounds, e. g., vinyl chloride-vinyl acetate copolymer,

vinyl chloride-acrylonitrile copolymer, vinyl acetateacrylonitrile copolymer, vinyl chloride-vinyl acetatemaleic anhydride terpolymer, vinyl chloride-methyl vinyl ether copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-trichloroethylene copolymer, styreneacrylonitrile copolymer. Also, saturated materials such as polyethylene terephthalate (Dacron) thermoplastic 4 I alkyd resins, .e. 'g., ethylene glycol adipate, etc. may be used.

The plunger should be heated enough that the thermoplastic binder will flow sufliciently during the contact time. Generally, the temperature of the plunger is 200 F. to 300 F.

Conventional molding pressures are employed, e. g., 20 to 100 lb./sq. in.

Instead of, or in addition to, using a heated plunger, the closure shell can be placed on a heated platen in order to aid in melting the polyethylene. The temperature of the platen can be between 200 F. and 300 F.

What is claimed is:

1. A container closure having a liner of granular cork bonded together by polyethylene.

2. A crown type closure comprising a shell having a fluted skirt and an inner liner of granular cork bonded together by polyethylene.

3. A crown closure as in claim 2 wherein the closure shell is made of metal, the metal has an inner coating of lacquer and the polyethylene also is present 'as an overall exterior coating for the cork.

4. A container closure having a liner composed of 10 to 87.5% granular cork bonded together by to 12.5% polyethylene.

References Cited in the file of this patent UNITED STATES PATENTS 2,196,407 Atkinson Apr. 9,, .1940 2,317,328 Kinney Apr..20, 1943 2,400,139 Roland May 14, 1946 2,551,087 Barnhart et a1 May 1, 1951 2,654,913 Maier Oct. 13, 1953 2,684,774 Aichele July 27, :1954 2,705,536 Phreaner Apr. 5,, 1955 

4. A CONTAINER CLOSURE HAVING A LINER COMPOSED OF 10 TO 87.5% GRANULAR CORK BONDED TOGETHER BY 90 TO 12.5% POLYETHYLENE. 